The present invention relates to a cleaning apparatus.
During the conventional process of fabricating a semiconductor device, a cleaning apparatus for cleaning a semiconductor wafer or LCD substrate is used. In a typical example of such a cleaning apparatus, a plurality of processing tanks for cleaning are arranged in a row, and at either end of this row of processing tanks is provided a loader portion and an unloader portion. A conveyor mechanism for passing and conveying the semiconductor wafers between the processing tanks is provided along one side of the row of processing tanks. Semiconductor wafers are removed from wafer carriers in the loader portion and are cleaned by being immersed by the conveyor mechanism into each of the processing tanks in turn. The unloader portion is configured to take the semiconductor wafers from the processing tanks after the cleaning is completed, and store them in wafer carriers.
The processing tanks are filled with distilled water or chemicals for cleaning such as hydrogen peroxide (H.sub.2 O.sub.2) or sulfuric acid (H.sub.2 SO.sub.4). If, for example, H.sub.2 SO.sub.4 is used for cleaning semiconductor wafers, the H.sub.2 SO.sub.4 is heated to a high temperature such as 150.degree. C. for the cleaning. Therefore, at least the processing tanks containing this chemical are provided with a dilutent liquid supply mechanism that supplies a dilutent (such as water) to dilute and cool the waste liquid expelled from the processing tanks and other parts of the cleaning apparatus, and a waste liquid sump (a trap tank) for temporarily storing this waste liquid. This method of temporarily storing diluted waste liquid in the trap tank, for example, is intended to improve operating safety by allowing the waste liquid to overflow from within this trap tank and drain into the waste liquid system of the factory.
However, in the above-described conventional cleaning apparatus, if, for example, the processing tank that uses high-temperature sulfuric acid for cleaning should be damaged and a large quantity of a chemical such as sulfuric acid at a high temperature should flow into the trap tank, the heat possessed by that chemical and the reaction heat concomitant with the dilution will increase the temperature of the waste liquid in the trap tank. Therefore, high-temperature chemicals will flow out of the trap tank into the factory's waste liquid system, and there is the danger that piping and other parts of the waste liquid system that are made of materials with a low thermal resistance (such as PVC) will be damaged.
This cleaning apparatus also requires piping systems for supplying and carrying away liquids such as processing liquids.
The processing tanks of the cleaning apparatus are provided with supply piping systems that supply the processing tanks with liquids for purposes such as cleaning or rinsing, such as distilled water, hydrogen peroxide (H.sub.2 O.sub.2), and sulfuric acid (H.sub.2 SO.sub.4). They are also provided with drainage piping systems that drain these liquids from these tanks or circulation piping systems that circulate the liquids back into the processing tanks via filters, and large numbers of piping joints are used in these piping systems and elsewhere to connect these pipes.
These piping joints are provided with pipe connection portions for connecting pipers to end portions of joint bodies that are configured in straight-through, L-shaped, or T-shaped forms. These pipe connection portions are also configured with pipe-fixing screw portions that are formed as male screw threads. Screw members (female screw threads) on nuts or other tightening devices engage with these pipe-fixing screw portions and are tightened therewith to fix the pipes to the joint bodies.
However, in a cleaning apparatus of this type, vibration of the pumps that are used to circulate the processing and other liquids, or the effects of the temperature or pulsations in the high-temperature processing liquids circulating therein, could loosen the tightening screw parts of the nuts and other parts of the piping joints, and this could result in the processing and other liquids leaking out of the processing tanks.